Moving blades of turbomachines, in particular gas turbines, are susceptible to oscillations, as a result of their elasticity and excitation, in particular due to the working fluid flowing through them as well as mechanical vibrations. If natural frequencies of the moving blades are excited, the resonance may cause damage to the turbomachine, in particular to the moving blades, and thus reduce the service life.
U.S. Pat. No. 2,862,686 therefore proposes to provide moving spheres inside hollow blades. Throughout the entire operation, the centrifugal force presses the spheres in their wedge-shaped guide radially to the outside, where they form a rib and thereby stiffen the blade. If the blade expands as a result of heating, the spheres subsequently slide on the inner wall of the blade cavity and thus adapt thereto. The spheres are designed exclusively with regard to the stiffening effect.
A blade system is known from DE 10 2009 010 185 A1 of the applicant. Accordingly, disk-shaped damping elements, which are freely movably situated in cavities in the blade system, carry out frictional knocks against each other and against the inner wall and dissipate oscillation energy from the system in this way. The damping elements in this case are designed with regard to their damping effect.